When it comes to medieval times and RPGs set in the middle ages you cannot get much more iconic than the drawbridge. The drawbridge is a type of movable bridge that protects the entrance to a castle or keep in conjunction with a moat or trench. In the early days before the chain and hinge drawbridge there were collapsible bridges, wooden or stone bridges with a built in weak point which when pulled or otherwise dislodged would bring down the entire structure. There was one major issue. Once the bridge was collapsed it was gone. These bridges quickly fell out of favor once the hinged and infinitely reusable drawbridge was developed.
Consisting usually of wood banded with iron and studs drawbridges were placed just outside a main gatehouse at the entrance of the castle. When raised the bridge would be flush again the wall and gate of the castle which consisted usually of more wood banded with iron and at least one or more portcullises. The bridge could be raised or lowered using a chain or rope pulley system until the more sophisticated counter-weight system was produced.